Method for positively determining the location of a drill string



Nov. 30, 1965 c. F. M LAREN, JR

METHOD FOR POSITIVELY DETERMINING THE LOCATION OF A DRILL STRING Filed Aug. 9, 1963 RECORDER DRILL PIPE l9 INVENTOR. CORNELIUS F.Mc LAREN,JR

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Nov. 30, 1965 c. F. M LAREN, JR 3,220,495

METHOD FOR POSITIVELY DETERMINING THE LOCATION OF A DRILL STRING 2 Sheets-Sheet 2 Filed Aug. 9, 1963 ATTORNEY.

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MILLED OUT WINDOW WHIPSTOCK COLLAR SHEAR PIN llfl fil 4 CORNELIUS F. MCLAREN,

JR.,INVENTOR United States Patent 3,220,495 METHOD FOR POSITIVELY DETERMINING THE LOCATION OF A DRILL STRING Cornelius F. McLaren, Jr., Andrews, Tex., assignor, by

mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed Aug. 9, 1963, Ser. No. 301,093 1 Claim. (Cl. 17545) The present invention relates generally to a method for locating tubing or other dense, metal objects positioned Within or outside of a borehole. More particularly, it concerns a method for positively determining whether a drill string is inside or outside of the lower section of a parted and/ or collapsed well pipe. Such information is important when attempting to restore former communications through damaged casing pipe. Also, this information is especially useful and necessary preliminary to conducting operations for re-entering damaged casing pipe in a well in order to remove any fish, such as drill pipe or other tubular goods, as well as to prepare the re-entered parted or damaged casing for running of smaller diameter casing to restore use of the original borehole. A re-entry operation of this nature and restoration of the original pipe communications are described and claimed in US. patent application Serial No. 301,058, filed August 9, 1963, by D. A. North, entitled Method for Re-entry of Damaged Well Pipe. The present invention will be described in conjunction with this re-entry procedure; however, it is to be understood that the invention is not to be considered as limited to re-entry work.

Frequently, well casing pipeparts and/ or collapses during drilling or production operations, and when this occurs, much effort and money are expended in an attempt to restore the former communications through the damaged casing pipe. Very often such communication is never re-established and the hole is lost.

Once oil field casing collapses or parts, it is conventional procedure to attempt to mill or drill through the damaged section and hope that the lower section of pipe below the damaged section is still in alignment with the upper casing above the damaged zone. Occasionally it is possible to drill into the casing below the damaged zone with no difficulty, remove any fish in the lower section of casing and run a small remedial string of casing if one is needed. Generally, however, the lower section of casing is missed and the drilling oftentimes results in cutting a new hole alongside the lower section of casing. When this occurs, the new hole is filled with cement and drilling is resumed in a trial and error attempt to communicate to the inside of the lower section of casing.

In each attempt to communicate to the inside of the lower section of casing, it is important to know whether the attempt has been successful, and the present invention provides a method for rapidly and accurately giving this information.

The hole is slowly and carefully redrilled using light bit weight and because the material surrounding the pipe is less dense or less hard than the formation material, the bit will preferentially drill in a part of the old original hole and immediately adjacent to the immobilized lower section of easing below the damaged zone.

In determining whether the drill pipe is outside of or within the casing pipe, a well known radioactivity pipe locator technique is employed. In this technique, which has been used in the past to orient the firing direction of gun perforators, a tool containing a source and detector of radiation, either or both of which are focused or collimated, respectively, is rotated through a 360 traverse and the angular positions of adjacent pipe strings are detected and recorded relative to the location of the tool.

I Operating in Wells.

3,229,435 Patented Nov. 30, was

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When used with gun perforating, the angular positions of the pipe strings are established relative to the angular direction of pipe detection which is fixed relative to the firing direction of the perforator. This tool and its use in gun perforating operations is described in US. patent application Serial No. 780,524, filed December 15, by Harry S. Arendt, entitled Method and Apparatus for Additional descriptions of similar tools and their operations are found in the Composite Catalog of Oil Field Equipment and Services, 24th Ed., 196l62, vol. 3, page 4862, under the title Oriented Perforating and the 25th ed., 1962-63, vol. 2, page 2938, under the title Nuclear Orientor.

The method of the invention provides a novel way to establish that the drill pipe lies outside of damaged casing pipe. It is necessary to know this prior to attempting reentry of the lower section of damaged casing pipe by milling a window in the lower section of the damaged casing pipe using a whipstock affixed to the lower end of the drill string and properly oriented with respect to a radioactivity pipe locator tool similar to the ones used and described above, but modified to operate with the directionally fixed whipstock. After the window is milled, any fish in the lower section of casing may be removed before running through the upper and lower sections of easing pipe and through the new by-pass passageway, a new, smaller diameter casing pipe and cementing it in place. A special orienting sub, connected in the drill pipe, cooperates with means on the modified pipe locator tool to fix the position of the tool with respect to the position of the whipstock.

Thus, a primary object of the present invention is to provide an improved, positive technique for locating the presence of tubing or other metal objects positioned within or outside of a borehole. A more specific object of the invention is to determine that a drill string is outside a damaged casing pipe preliminary to re-entering the damaged casing pipe to remove fish and/or to set a new casing string after re-en-try.

The above objects and other objects and advantages of this invention will become more apparent in the following, more detailed description of the invention when taken with the drawings in which:

FIGS. 1 to 6 are vertical, partly sectional views of a borehole illustrating sequential steps of the method of the invention as well as its use in conjunction with the re-entry and repair of damaged casing pipe.

In FIG. 1 is shown a conventional surface wellhead apparatus 10 from which is suspended a conductor casing pipe 11 cemented in place by cement 12 and a deeper set casing pipe 13 cemented in place by cement 14. Casing pipe 13 has parted and collapsed as indicated at 15, and the lower portion of a drill pipe 16 is shown contained partly Within the lower fish portion 17 of casing 13, and in the open hole 18 below the lower end of parted casing 13.

As seen in FIG. 2, a tubular string such as drill pipe 19 is lowered through the upper part 20 of damaged casing pipe 13, and an attempt is made to drill into the lower fish portion 17 of the casing pipe. Drill pipe 19 drills to a preselected or predetermined depth sufficient to insure that the drill pipe has either entered the lower portion 17 of the casing pipe or is positioned alongside it.

In this position, as seen in FIG. 3, a pipe locator tool 21 is suspended in drill pipe 19 by a conductor cable 22 connected to a surface recorder 23. Tool 21 (or pipe 19 if tool 21 is fixed immovably within pipe 19) is then rotated 360. If as is shown in FIG. 3, drill pipe 19 is positioned alongside the fish portion of easing pipe 17,

then the presence of casing pipe 17 will be indicated on recorder 23. If, however, drill pipe 21 drilled into and 3. was positioned within the casing pipe 17, then no indication of pipe adjacent pipe locator tool 21 would be recorded on recorder 23 when the pipe locator tool 21 was rotated. In this latter event, new casing pipe might be run and the communication re-established through known procedures.

As an example of this technique in an actual field operation, a well had 8% inch casing pipe part at 3,152 feet with the top joint of the lower fish'collapsed with its top at 3,154 feet. The pipe locator survey was run after 7% inch washpipe and 7% rotary shoe had drilled to about 3,192 fee-t (past a casing collar at 3,181 feet). Two and one-half inch tubing was then run to 3,192 feet and the pipe locator survey clearly indicated that the 2 /2 inch tubing string was outside the 8% inch casing pipe fish.

When it is determined that drill pipe 19 is not within casing pipe 17, pipelocator tool 21 may be removed from the well and additional attempts may be made to drill into casing pipe 17. At each attempt, the pipe locator tool 21 is lowered in drill pipe 19 to determine whether the drill pipe is outside of or within casing pipe 17. If desired, once .it is established that the drill pipe 19 is outside casing pipe 17, a remedial operation may be carried out to re-enter casing pipe 17, to remove fish located therein, and to restore communications by setting a new, smaller casing pipe. These operations are described in greater detail below Referring to FIG. 4, on the lower end of drill pipe 19 is arranged a special orienting sub, shown and described in detail in the North application supra, just above bit 24. A whipstock 28 is fastened to hit 24 by shear pins. Then the drill pipe with its orienting sub and whipstock is run through the upper parted portion 20 of easing pipe 13 to the bottom of the newly drilled hole 29.

Sub 27 is formed with a cam surface and a groove, designed to position a pipe locator tool, also shown and described in detail in the North application supra. The pipe locator tool includes a collimated detector and a focused source of radiation separated by shielding means. A positioning lug on this tool is aligned with the collimated detector or focused source in a fixed or known angular position relative thereto. The face of the whipstock 28 is aligned with the groove on sub 27 or in a fixed, predetermined angular position relative to the angular position of the groove.

The pipe locator toolis lowered through drill pipe 19 on a conductor wire line connected toa surface recorder until the cam surface guides the lug into the groove in sub 27. Then drill pipe 19 is raised off bottom to permit rotation of the drill pipe and drill pipe 19 is rotated to permit the pipe locator tool to detect and locate casing pipe 17 relative to the face of whipstock 28 which is then aligned with the casing pipe 17. The drill pipe 19 is then lowered and the whipstock 28 firmly imbedded in the cement 14. Slackotf of additional weight of drill pipe 19 shears the mill 24 free of the now oriented whipstock and the drill pipe is free to turn the mill against the side of the casing 17. A window 40 is cut in the easing pipe 17 as shown in FIG. 5 by mean-s of the drill pipe 19 and the mill 24. The new bypass passageway is then preferably reamed and enlarged and smoothed out as desired. Any fish in the lower part of the now communicated to casing 17, such as a drill pipe fish 16, then may be removed by conventional fishing techniques. As seen in FIG. 6, a smaller string of new casing 41 is run through the larger casing 20 and lower portion thereof 17, through the by-pass passage 29. Although not shown, the smaller casing then is cemented in place by conventional cementing techniques.

Having fully described the method, apparatus, objects, and operation of my invention, I claim:

A method for positively determining whether a drill string has drilled into the lower, undamaged section of a damaged well pipe comprising the steps of lowering drilling means including a drill string into the upper, undamaged section of said well pipe;

drilling with said drilling means through the upper section of said well pipe and beyond to a preselected depth below the upper end of the lower section of said well pipe;

lowering a pipe locator means, capable of detecting,

when operated, the presence of said well pipe when said well pipe is located alongside of said drill string, to the lower end of said drill string when said drill string is located at said preselected depth; and

then operating said pipe locator means to detect the presence of said well pipe, detection of the presence of said well pipe by said pipe locator means establishing that said drill string is located outside of the lower section of said Well pipe and failure to detect the presence of said well pipe by said pipe locator means establishing that said drill string is within the lower section of said well pipe.

References Cited by the Examiner UNITED STATES PATENTS 8/1961 True 166-5S 9/1963 Kenneday et al 16655.1

OTHER REFERENCES CHARLES E. OCONNELL, Primary Examiner. 

